Synergistic antioxidants and their use



SYNERGISTIC ANTIOXIDANTS AND THEIR USE Edgar Bradley Oldenburg, Royal Oak, Mich., assignor to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application March 13, 1953, Serial No. 342,265

3 Claims. (Cl. 44-64) The present invention relates .to the protection of materials that are subject to deterioration by contact with oxygen in any of its forms.

Certain hydrocarbon-type materials in wide use are subject to deterioration, sometimes fairly rapidly, when exposed to air and particularly Where the air might have some ozone content. By way of example, gasolines and diesel engine fuels now enjoying widespread use are for practical reasons manufactured with a relatively high content of olcfinic-type hydrocarbons. These materials, upon standing, will react with oxygen and will at least be partially converted to a form that is not desirable. Thus, olefinic gasolines will show a strong tendency to deposit gums which will interfere with the filtering of the gasoline by clogging up the filters and even cause fuel-passing valves to stick. In addition, gummy deposits often foul spark plugs and thereby cause misoperation of the engine. These same difiiculties are experienced with diesel fuels,

In the past it has been found desirable to add antioxidants to the above types of oxygen-sensitive materials. However, with the progress of time, fuels have come to contain more and more olefins and engines have become more efiicient and powerful so that the engine and fuel specifications are more rigid. The continued use of prior art antioxidants accordingly results in the buildup of the antioxidant concentration to the point where it cannot be tolerated by some engines.

Among the objects of the present invention is the provision of novel antioxidant compositions that are more effective than the prior art antioxidants.

Additional objects of the invention include the provision of mixtures of olefin-type hydrocarbons with a synergistic antioxidant composition that makes possible more efiective protection of the hydrocarbons.

The above as well as still further objects of the present invention will be more clearly understood from the following description of several of its exemplifications.

It has been discovered that standard antioxidants selected from the class consisting of phenylenediamines, aminophenols and trialkylphenols, when mixed with a compound of the class consisting of alkoxy and alkylamino chrysoidines, show an unexpectedly high antioxidant efiect in protecting olefin-type hydrocarbons that are subject to deterioration by oxygen. This eifect is particularly significant inasmuch as alkoxy and alkylamino chrysoidines show very little antioxidant value in connection with these materials. The synergistic eflfect appears to extend to antioxidant composition having from to 80 percent of alkoxy and alkylamino chrysoidines, the balance being essentially one or more of the abovenamed standard antioxidants. Best results are obtained, however, with an antioxidant composition having about twice as much of the standard antioxidant as alkoxy and alkylamino chrysoidines.

The following examples are typical of the improvements resulting from the present invention. In these examples the deterioration tendency has been measured atent o 2,766,106 Patented Oct. 9, 1956 by determining the induction period various samples of materials require before beginning to react with oxygen under accelerated reaction conditions. The specific method used is a standard one adopted by the American Society for Testing Materials for determination of the Qxidation Stability of Gasoline (Induction Period Method), ASTM Designation: D525-46, and is fully described iii Part III-A, ASTM Standards for 1946. According to this method, the induction period is the period during which there is no absorption of oxygen by the test m'alterial as indicated by a time delay before the pressure drops in a testing bomb containing the test material at 100 C. with oxygen at an initial pressure of 100 pounds per square inch gauge.

With a standard commercial gasoline having the following charaoteristics and with an induction period of 50 minutes, 0.00375 percent of N,N'-di-sec-butyl-p-phenylenediamine increases the induction period to 380 minutes, 0.0075 percent of this antioxidant increases the induction period to 585 minutes, whereas the substitution of paraethoxy chrysoidine for one-third of the above antioxidant increases the induction period to 440 and 715 minutes respectively. The paraethoxy chrysoidine has by itself an etfect which is only about one-tenth that of the N,N'-di-sec-butyl-p-phenylenediamine.

The gasoline characteristics were:

Hydrocarbon type (percent by volume):

Distillation range, F.

(29.3 inches of mercury):

Initial 104. s 139. 10 153. 15 163 20 179 30 192 40 213 so 234 60 256 70 277. so 299 as 312 326 342 Final 37s The above synergistic efiects are also obtained with other alkoxy chrysoidines, as well as with alkylamino chrysoidines. Several of these alternative chrysoidines are:

Orthomethyl- Metabutyl- Ortho, para-dimethoxy- Paraoctaoxy- Orthoisopropylamino- Ortho, para-bis(dimethylamino) Metaamylamino- It appears that any alkoxy or alkylamino chrysoidine is suitable where the alkyl groups have up to ten carbon atoms each, whether one or more alkoxy or alkylamino groups is present, or in the case of alkylamino groups whether one or more of the alkyl substituents are attached to the same amino nitrogen,

The alkoxy or alkylamino chrysoidines employed according to this invention 'have the general formula in which A and B can be the same or diiferent and are selected from the group consisting of hydrogen, alkoxy containing up to carbon atoms, monoalkylamino containing up to 10 carbon atoms, and dialkylamino containing up to 10 carbon atoms in each alkyl radical; and where not more than one of A and B is hydrogen. Thus, the chrysoidines of the invention contain on one phenyl radical the radicals A and B as defined above, and on the other phenyl radical unsubstituted amino groups in the ortho and para positions thereof.

The above compounds can be made in any desired manner as for example by diazotizing the corresponding alkoxy or alkylamino aniline and then coupling the diazotized product with metaphenylenediamine. The specific details of this general method of preparation are well known and reference can be made to any manual of organic chemistry.

When other of the above-mentioned prior art standard antioxidants are substituted for the N,N-di-sec-butylphenylenedi-amine, equally good synergistic improvement is obtained. Specific examples of suitable prior art antioxidants showing the synergism are unsubstituted pphenylenediamine, unsubstituted o-phenylenediamine, and oand p-phenylenediamines in which either or both amine groups are alkylated as for example N,N'-diethyl-pphenylenediamine, N-amyl-p-phenylenediamine, N-methyl-N'-n-propyl-p-phenylenediamine, N-decyl-p-phenylenediamine, N-methyl-N-lauryl-p-phenylenediamine, N,N'- diethyl-o-phenylenediarnine, N propyl o phenylenediamine, N-butyl N isopropyl o phenylenediamine, N- stearyl-o-phenylenediamine, N-methyl-N'-lauryl-o-phenylenediamine, unsubstituted p-aminophenol, unsubstituted o-aminophenol, unsubstituted m-aminophenol, any of the above aiminophenols in which the amino nitrogen is substituted with an alkyl group ranging from methyl to cetyl, 2,4-dimethyl-6-tertiary-butyl-phenol, similar 2,4,6- trialkylphenols in which some or all of the alkyl groups are the same, or they are all different, and the groups range from methyl to lauryl.

Although the above examples show the value of the present invention in connection with a stock gasoline, the same general improvements are obtainable with other gasolines as well as with olefin-type diesel fuels that tend to deteriorate in the presence of oxygen. The elfect with gasolines is obtained whether or not the gasoline is colored with dyes or leaded, that is, contains added tetraethyl lead along with its usual lead scavenger complement, as for example ethylene dibromide or ethylene dichloride. In the case of leaded gasoline an additional factor warrants consideration. It has been found that the addition of organolead antiknock agents such as tetraethyl lead to certain inherently stable hydrocarbon fuels, that is, fuels containing only very small quantities of olefinic and other readily oxidizable constituents results in the formation of a fuel composition which tends to deteriorate prematurely in the presence of oxygen or ozone. However, it has been found that such an inherently unstable fuel composition can be protected against such deterioration by blending therewith the synergistic antioxidant compositions of the present invention. In this embodiment the amount of the synergistic mixture employed is contingent upon both the nature of the hydrocarbon fuel and the amount of organolead antiknock agent employed therein. It has also been found that in some cases it is advantageous to provide organolead-containing mixtures comprising the synergistic antioxidant compositions of the present invention. That is to say, to facilitate blending operations it is often efiicacious to provide antiknock fiuids containing the synergistic antioxidant compositions of the present invention. In this manner the protection against the adverse elfects of oxygen is alforded both to the antiknock fluid itself and to the resulting leaded fuel composition.

With all of the above chrysoidines, about the same formulation is effective to produce the desired synergistic results. The concentration of antioxidant mixture in the material being protected can be varied from about 0.01 percent down to the smallest concentration that will be effective. Concentrations larger than 0.01 percent can be used but are not desirable. With present day gasolines, at least about 0.005 percent of the new mixture is preferred.

A feature of the present invention is that it reduces the solubility problems arising when the separate ingredients of the mixture are used independently. Thus, not only is the antioxidant effect of any given percentage of addition increased, but moreover the amounts of the individual ingredients are even further reduced so that they are more readily dissolved in the gasoline or other hydrocarbon fuel. Solvents such as ethanol, acetone or the like can be used to further improve the solubility of the synergistic mixture without significantly afiecting the above described results. The mixtures of the present invention can be dissolved as a fairly highly concentrated solution in these solvents and then readily mix with the hydrocarbon fuel to give a uniformly dispersed product from which the antioxidants do not settle out. About 1 percent of the solvent based on the weight of the final gasoline formulation can be so incorporated.

All percentages given above are by weight unless otherwise specified.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope hereof, it is to be understood that the invention is not limited to the specific embodiments hereof, except as defined in the appended claims.

What is claimed is:

1. An unstable gasoline containing an organolcad antiknock agent which increases its deterioration in the presence of oxygen, and in a quantity sufficient to inhibit the deterioration of the gasoline, a synergistic antioxidant mixture consisting essentially of an N,N'-dialkylphenylenediamine in which each alkyl group has from 1 to 12 carbon atoms and a chrysoidine in which one phenyl radical is substituted with two members from the group consisting of hydrogen, alkoxy containing up to 10 car bon atoms, monoalkylamino containing up to 10 carbon atoms, and dialkylamino containing up to 10 carbon atoms in each alkyl radical, not more than one of said members being hydrogen; and in which the other phenyl radical contains unsubstituted amino groups in the ortho and para positions, said antioxidant being present in amount of about 20 to 90 percent by weight of said antioxidant composition, the chrysoidine being from about 10 to percent of said mixture.

2. An olefinic gasoline containing in a quantity sufficient to inhibit the deterioration of the gasoline, a synergistic antioxidant mixture consisting essentially of a mixture of an N,N'-dialkyl-phenylenediamine in which each alkyl group has from 1 to 12 carbon atoms, and a chlysoidine in which one phenyl radical is substituted with two members from the group consisting of hydrogen, alkoxy containing up to 10 carbon atoms, monoalkylamino containing up to 10 carbon atoms, and dialkylamino containing up to 10 carbon atoms in each alkyl radical, not more than 'one of said members being hydrogen and th e References Cited in the file of this patent UNITED STATES PATENTS Ostromislensky Aug. 17, 1937 FOREIGN PATENTS Great Britain Nov. 17, 1932 

1. AN UNSTABLE GASOLINE CONTAINING AN ORGANOLEAD ANTIKNOCK AGENT WHICH INCREASES ITS DETERIORATION IN THE PRESENCE OF OXYGEN, AND IN A QUANTITY SUFFICIENT TO INHIBIT THE DETERIORATION OF THE GASOLINE, A SYNERGISTIC ANTIOXIDANT MIXTURE CONSISTING ESSENTIALLY OF AN N,N''-DIALKYLPHENYLENEDIAMINE IN WHICH EACH ALKYL GROUP HAS FROM 1 TO 12 CARBON ATOMS AND A CHRYSOIDINE IN WHICH ONE PHENYL RADICAL IS SUBSTITUTED WITH TWO MEMBERS FROM THE GROUP CONSISTING OF HYDROGEN, ALKOXY CONTAINING UP TO 10 CARBON ATOMS, MONOALKYLAMINO CONTAINING UP TO 10 CARBON ATOMS, AND DIALKYLAMINO CONTAINING UP TO 10 CARBON ATOMS IN EACH ALKYL RADICAL, NOT MORE THAN ONE OF SAID MEMBERS BEING HYDROGEN; AND IN WHICH THE OTHER PHENYL RADICAL CONTAINS UNSUBSTITUTED AMINO GROUPS IN THE ORTHO AND PARA POSITIONS, SAID ANTIOXIDANT BEING PRESENT IN AMOUNT OF ABOUT 20 TO 90 PERCENT BY WEIGHT OF SAID ANTIOXIDANT COMPOSITION, THE CHRYSOIDINE BEING FROM ABOUT 10 TO 80 PERCENT OF SAID MIXTURE. 